Automatic gas burner with variable flame port area



J. A- HARRISON 3,223,142

AUTOMATIC GAS BURNER WITH VARIABLE FLAME PORT AREA I Dec. 14, 1965 5 Sheets-Sheet 1 Original Filed March 9, 1959 INVENTOR.

JAMES A bfl/PR/JO/V BY ewzn a fiwuw Dec. 14, 1965 J. A. HARRISON 3,223,142

AUTOMATIC GAS BURNER WITH VARIABLE FLAME PORT AREA Original Filed March 9, 1959 5 Sheets-Sheet 2 IN V EN TOR.

JAMAs A flmwP/sou BY Dec. 14, 1965 J. A. HARRISON AUTOMATIC GAS BURNER WITH VARIABLE FLAME PORT AREA 5 Sheets-Sheet 5 Original Filed March 9, 1959 a0 a o l O 4 0 4 i a A H a w w. 2 u

2 .F f a E u a. o M o a 1 27 a n1 5 m 6- Paula/1:

4 fro/Mfrs United States Patent 3,223,142 AUTUMATIC GAS BURNER WITH VARIABLE FLAME PORT AREA James A. Harrison, 24450 Telegraph Road, Southiield, Mich.

Continuation of abandoned application Ser. No. 798,186, Mar. 9, 1959. This application Nov. 19, 1962, Ser. No. 239,103

15 Claims. (Cl. l581l7) This application is a continuation of my co-pending application Ser. No. 798,186, now abandoned.

This invention relates to an automatic fuel gas heater. Disclosed in my US. Patent No. 2,836,409 is an automatic fuel gas heater which, while economically satisfactory for large installations, is frequently too costly for smaller installations such as small to medium size restaurants, assembly halls, small shops, etc. The heater disclosed herein is admirably suited to the latter installations, but not limited in application thereto, as manufacturing, installation, and service costs may be kept relatively low.

The basic inventive concept disclosed in the instant application, and common to the various embodiments shown and described herein, is the idea of providing a plurality of individual combustion air streams, and gas escape orifice means positioned to direct fuel gas into the individual air streams at the point of minimum static pressure of each air stream, and fuel gas control valve means for varying the effective length of the gas stream; wherein the air streams are arranged along the direction of variable length of the fuel gas stream whereby the number of individual air streams with which fuel gas is mixed varies in direct relation to the rate of fuel gas delivery, and the gas and air are brought together at the point of minimum static pressure of each air stream. This basic idea is also common to my copending United States application Serial No. 154,995, filed November 27, 1961, now abandoned.

The invention as disclosed herein is embodied in a heater of the direct fired, makeup air type, i.e., fuel gas is burned directly in the air to be heated which is drawn from outside and blown into the space to be warmed. The heater is responsive to the temperature of the space being warmed, or the air stream issuing from the heater, or both, and serves to regulate accordingly the amount of fuel gas burned.

As is well known to those skilled in the art, in order to sustain combustion, the pressure of the fuel gas delivered to a burner must be kept above a certain minimum. It is also appreciated that as the amount of fuel gas passing to a burner is progressively reduced, as by closing a valve in the gas line, the pressure drops more rapidly than does the volume of gas delivered to the burner; and that in order to reduce the volume of gas the desired amount it may be necessary to close the valve so far that the gas pressure drops below the minimum flame-sustaining pressure and the burner will flash back. If a pilot flame is disposed adjacent the burner, and the burner flame is extinguished, the burner will pop in an irritating and inefficient fashion as the pilot tries to relight the gas issuing from the burner.

One, though more expensive, arrangement for overcoming this difliculty is disclosed in the aforesaid patent where a plurality of burner tubes or the like are arranged in fuel gas receiving relation along a serially apertured gas manifold. Fuel gas is fed to the manifold to discharge from the apertures to the burner tubes. A motor driven piston in the manifold, shiftable therealong toward and away from the gas inlet and positioned in response to temperature variations, serves to open a greater or lesser number of the apertures as it is positioned along the manifold to vary the volume of fuel gas delivered to the burner tubes while allowing the gas pressure to remain constant.

In one embodiment of the instant invention the piston is in the form of a spool valve or the like which is urged with a uniform restoring force along the manifold toward the manifold gas inlet thereby tending to reduce to a minimum the number of outlet ports between the gas inlet and the spool, but with the spool responsive to an increase in the pressure of fuel gas within the manifold to shift away from the fuel inlet and expose a greater number of outlet ports to the gas. An increase in the fuel gas pressure within the manifold may be caused by opening to a greater extent a valve in the gas feed line to the manifold. The number of outlet ports exposed by the spool will be automatically determined by the restoring force of the spool as only that number of ports will be exposed which are sufficient to allow the escape of fuel gas at a rate maintaining the gas pressure in the manifold equal to the restoring force of the piston. This arrangement eliminates the requirement of a motor drive to position the piston and permits the firing rate of the heater to be controlled by a temperature responsive valve in the gas feed line to the manifold.

The primary object of the invention is the provision of a simple and inexpensive automatic fuel gas heater having a widely variable firing rate which may be controlled merely by the progressive opening and closing of a valve in the fuel gas line and which heater is quiet and efficient in operation.

Another object of the invention is the modification of the arrangement disclosed in the aforesaid patent by eliminating the requirement of positioning the piston by the action of a temperature responsive motor control system coupled to the piston to position the same in the manifold.

A further object of the invention is the provision of a fuel gas manifold assembly which will discharge fuel gas for use in a burner assembly at a constant pressure though the volume of fuel gas delivered to the manifold is variable.

An important object of the invention is the provision of an automatic fuel gas heater which includes port means for dividing combustion air flowing through the heater into a plurality of individual air streams, fuel gas delivery means defining a gas passageway opening through a gas escape orifice directing fuel gas into the air streams at the point of minimum static pressure of the air streams for mixing the gas and air, and a gas control valve for controlling the rate of gas flow into the gas passageway to thereby vary the efiective length of the fuel gas stream, with the air ports arranged along the direction of variable gas stream length so that the number of air streams to which gas is delivered is varied in direct relation to the rate of gas delivery.

Other objects, advantages, and meritorious features will more fully appear from the specification, claims, and accompanying drawings, wherein:

FIG. 1 is a vertical section taken through the fuel gas heater embodying my invention;

FIG. 2 is a cross sectional view taken on the line 22 of FIG. 1;

FIG. 3 is a cross sectional View taken on the line 3--3 of FIG. 2;

FIG. 4 is an end view looking toward the gas discharge end of the burner assembly shown in FIG. 3;

FIG. 5 is a modification of the burner assembly shown in FIGS. 3 and 4;

FIG. 6 is a cross sectional view taken on the line 6-6 of FIG. 5;

FIG. 7 is a cross sectional view through another embodiment of the invention;

FIG. 8 is a cross sectional view through still another embodiment of the invention;

FIG. 9 is a cross sectional view taken on the line 9-9 of FIG. 8;

FIG. 10 is a perspective view of the piston-like valve used in the embodiment of FIG. 8;

FIG. 11 is a schematic representation of a horizontal fuel gas discharge manifold showing a source of air under pressure connected to one end of the manifold to react against the piston-like valve.

The invention is shown embodied in what in the trade may be termed a direct fired makeup type fuel gas air heater though its application is not necessarily limited to such type of heater, as will hereinafter be apparent to those skilled in the art. The heater shown in FIG. 1 includes a housing 10 closed at the sides, top, and bottom, but open at the front and rear as at 12 and 14. Disposed within the housing is a conventional centrifugal type blower generally indicated at 16 and driven in any suitable fashion as by electric motor 18 connected to the blower by a belt drive 20. As is well understood in the art, the blower creates a vacuum adjacent its rotational axis and blows air through the blower housing 22 for discharge outwardly of housing 10 through opening 14. The blower may be supported within housing 10 by a supporting bracket or the like 24. The partial vacuum created in housing 10 by the operation of blower 16 causes air to enter housing 10 through the opening 12 and pass to the blower so that a flow of air from opening 12 out through opening 14 is created by the blower 16 within housing 10. When used as a makeup air heater opening 12 will be arranged to draw air from outside the room or other space to be heated while opening 14 will be arranged to discharge the heated air into the room or space to be heated.

To heat the air flowing through housing 10, I provide a burner assembly generally indicated at 26 in FIG. 1 and a fuel gas manifold assembly generally indicated at 28. The manifold assembly serves to admit fuel gas to the burner assembly which, in turn, mixes such gas with a portion of the air flowing through housing 10 so that such air and gas mixture will burn along the downstream edge 30 of the burner assembly.

The fuel gas manifold comprises a vertically disposed elongate tube 32 extending across aperture 12 spaced inwardly therefrom as shown in FIG. 1. To the lower end of the manifold is connected a temperature responsive fuel gas control valve 34 to control the volume of fuel gas entering the manifold. Such temperature responsive valve is of conventional construction and purchasable from a number of valve suppliers. It includes a temperature responsive bulb or the like 36 connected to the valve and disposed in the air stream issuing from the opening 14. Bulb 36 may alternatively be positioned to respond to temperature changes within the space being heated rather than in the direct path of the air issuing from opening 14. Valve 34 is provided with a knob 38 for setting the valve to establish its temperature responsive range of operation and this, too, is of conventional construction and operation.

Valve 34 is connected to the lower end of the manifold tube 32 by piping including a pipe 40 and a four-way coupling 42. The four-way coupling 42 may be threaded- 1y connected to the lower end of the tube 32. The lefthand and bottom sides of the four-way coupling may be closed by plugs or nipple and cap connections such as indicated at 44 and 46. The upper end of the tube 32 is closed gas tight by a cap 48.

It is conventional in the installation of fuel gas burning equipment to provide a fuel gas pressure regulator upstream of the gas control valve and such is shown at 50. A manually operable gas shut-off valve 52 is disposed ahead of the pressure regulator.

As shown in FIGS. 2 and 3, the manifold tube 32 is provided at intervals spaced apart longitudinally along the tube with fuel gas discharge apertures 54. These apertures may be disposed and are shown here as disposed in staggered relation rather than lying along a common straight line extending longitudinally of the manifold tube. The purpose of this staggering will be hereinafter described. Slidably received within the manifold tube 32 is a piston-like valve element, generally indicated at 56, which is urged by a predetermined force toward the gas inlet at the bottom of the manifold. In the embodiment shown in FIG. 3, the weight of the valve element itself will serve to urge it downwardly through the manifold tube toward the gas inlet. The valve element 56 cooperates with the inner wall surface 58 of the manifold tube to provide a barrier against the uncontrolled escape of fuel gas upwardly through the manifold around the valve element. Because the valve element is free floating within the manifold tube and it is desirable to have the element slide freely vertically within the tube, a small amount of fuel gas may tend to escape around the element.

To prevent any appreciable escape of fuel gas around the element, the same is designed as a spool type valve having three longitudinally spaced-apart valve discs 6%), 62 and 64 secured to a valve stem 66. Any fuel gas tending to escape around the periphery of the disc 64 will be trapped by the disc 62. Any fuel gas escaping around the periphery of disc 62 will tend to be trapped by the upper disc 6!). The spacing apart of the disc 60, 62 and 64 is such in relation to the spacing of the apertures 54 that ordinarily any fuel gas trapped beneath discs 60 and 62 will tend to escape. from the manifold through apertures 54 between the discs. In the event any fuel gas does escape around the valve element 56, a portion thereof will pass outwardly through the apertures 54 above the element and will burn in the burner assembly by virtue of the piloting action of the gas flame therebelow. Tube 68 communicating at its upper end with the interior of the manifold and at its lower end, as shown in FIG. 1, with the bottom of the burner assembly, serves to allow fuel gas escaping around disc 64 when the valve is in its uppermost position, shown in dotted outline in FIG. 3, to be passed to the lower end of the burner assembly for ignition.

The valve stem 66, as shown in FIG. 3, is hollow to receive weights 70 for the purpose of varying the force with which the valve element tends to drop in the manifold toward the fuel gas inlet. The valve element 56 may descend in the manifold tube until striking the stop pin 72 received through a wall of the tube adjacent the lower end thereof. Upon the admission of fuel gas to the lower end of the manifold by an opening of the valve 34 in response to a determined drop in temperature of the air stream flowing out of opening 14, the weight of the valve element 56 will determine that amount of fuel gas pressure in the manifold necessary to lift the valve element. If valve 34 is merely cracked open so that a very small amount of fuel gas enters the manifold, the element 56 will remain seated upon pin 72 until the accumulation of fuel gas beneath it reaches such a pressure that the force of the fuel gas against the element will lift it to uncover the first discharge port 54. The element will uncover such port and allow the fuel gas beneath the element to escape through the port. The pressure of the fuel gas escaping from the port will be determined by the weight of the valve element and assuming that one port will be sufficient to allow fuel gas to discharge from the manifold at a rate maintaining the fuel gas pressure equal to the force of gravity acting on the element, the element will remain just above the port and allow gas to escape therefrom to the burner assembly.

It is apparent that the number of apertures 54 exposed to the fuel gas in the manifold is dependent upon the rate at which fuel gas enters the manifold from valve 50, and that the pressure escaping from the ports 54 of the manifold will be determined by the weight, or what might .5 be termed restoring force, of the valve element. Because of this the manifold assembly will maintain a uniform pressure of fuel gas issuing therefrom despite the fact that the volume of fuel gas entering the manifold may vary. This permits the regulation of the B.t.u. output of the heater by simply a progressive opening and closing of the gas valve 34 in response to temperature variations of the air stream without regard to the fact that closure of valve 34 would ordinarily ten-d to reduce the pressure of fuel gas issuing therefrom below the burner flame sustaining pressure.

The weight of the valve element must be such that it will only allow, under the influence of fuel gas pressure therebelow, ascent of the valve by an amount exposing such number of exhaust ports as will discharge gas therethrough at optimum burner flame pressure. The weights 70 in the hollow stem provide means for adjusting the restoring force of the piston so that proper burner flame gas pressure in the manifold may be maintained for any particular installation.

Disposed adjacent the manifold and in gas-receiving relation therewith is the burner assembly 26. Such assembly includes a staggered arrangement of burner tubes indicated in FIG. 4 at 74. These tubes are secured together as by welding or the like 76, which serves to integrate them to a unitary structure. The upstream ends of the tubes are spaced from the manifold as shown in FIG. 3 to allow the entry of both the gas from the discharge apertures 54 of the manifold as well as a portion of the air stream entering housing 10 through opening 12. In order to ensure an adequate supply and mixture of fuel gas and air, an air deflector or collector is provided which extends longitudinally of the burner assembly and embraces the manifold and burner tubes as shown in FIG. 2. Such collector comprises a pair of opposed shields or the like 78 and St) shaped as shown in FIG. 2 to catch a portion of the air stream and deflect it around the manifold and into the burner assembly. Each shield 78 and 80 is rigidly secured in any convenient fashion to the unitary assembly of burner tubes. The burner tubes are carried by shields 78 and 81 which are, in turn, fastened to the manifold as by screws or the like 82, which extend through spacers 84 disposed between the manifold and the shields. In this fashion the burned assembly is carried by the manifold. The manifold, as shown in FIG. 1, is in turn carried by the housing It) by virtue of the fact that the upper end of the manifold tube extends through an opening 86 in the top wall 88 of housing 10 while the cap connection 46 extends through a corresponding aperture in the lower wall 911 of the housing.

The burner tubes 74 in FIG. 4 are of tubular or cylindrical construction. Within their discharge ends is disposed flame retention means in the form of piloting grids 92. These grids 92 are in the form of gears provided with central apertures 94 through which the major portion of the fuel gas and air mixture passes. The spaces between the gear teeth, and indicated at 96, serve to allow a portion of the fuel gas and air mixture to pass around the grids adjacent the periphery thereof to pilot the gas and air mixture issuing from the central aperture 94. The coaxial alignment of apertures 94 and 54 is apparent from a consideration of FIG. 4.

Because of the staggered arrangement of the tubes 74- the discharge apertures 54 of the manifold are correspondingly staggered. The staggered arrangement of tubes 74 allows a greater number of burners to be incorporated in the burner assembly to receive fuel gas from the manifold than would be possible were the tubes to be disposed in line one above the other.

A modified form of burner assembly is shown in FIGS. 5 and 6. Such modified form is essentially the same as that shown in FIGS. 3 and 4 except that the burner tubes are of square or rectangular sectional shape rather than circular, and the flame retention means is of a somewhat different design. The modified tubes indicated at 98 are secured together in staggered relationship in any convenient fashion as by welding or the like (not shown) with the center line of each tube disposed in coaxial relation with one of the discharge ports 54 of the manifold. The deflection shields 78 and 80 are secured to the unitary assembly of tubes 98 with the relationship between the tubes and shields being similar to that shown in FIG. 2. Disposed in the downstream end of each tube is flame retention means or a piloting grid in the form of a square or rectangular barrier 101) having a square aperture coaxially aligned with the center line of the tube and indicated at 102. The outer edge of the barrier 10% is provided with a plurality of V-shaped notches 1114 which are arranged in threes at each edge of the barrier. The barriers are secured in the ends of the tubes in any convenient fashion. The notches 104 allow the passage of a small portion of fuel gas and air mixture to pilot the main burner flame issuing from the larger apertures 102. The cross sectional shape of the barriers M12 is shown in FIG. 6.

The lowermost burner tube of the burner tube assembly shown in FIG. 3 and indicated at 1116 serves as a standing pilot burner to pilot the burner tubes thereabove upon ascent of the valve element 56. Such burner tube is fed fuel gas from the pilot line 108 shown in FIG. 1. A shutoff valve 110 and a pressure regulator valve 112. are disposed in the line 108. The line 108 communicates through the side of the burner assembly with the interior of the burner tube 106 as shown in FIG. 3. Any fuel gas in tube 68 which may escape from the upper end of the manifold likewise issues from the discharge end of the burner tube 106 to burn along with the fuel gas from tube 108.

In FIG. 7 is disclosed a modification of the invention wherein the fuel gas manifold includes a horizontally disposed portion indicated generally at 114 and a vertically disposed portion 116. The advantage of the FIG. 7 embodiment over that heretofore described is that it allows the manifold to emit fuel gas in a horizontal plane rather than a vertical plane. Portion 114 of the manifold includes a pair of oppositely extending arms 118 and 120 each of which is provided with a series of spacedapart fuel gas discharge apertures 122. The downwardly extending portion 116 of the manifold is gas tight. The fuel gas inlet for the manifold indicated at 124 delivers fuel gas thereto at the junction between the downwardly extending portion 116 and the horizontal portion 114.

Slidably disposed within the portion 118 and 120 are piston-like valves 126 and 128 yieldingly biased by a weighted member 130 toward the junction between the portions 114 and 116. Each of the piston-like valves is connected to the weighted member 136 by a flexible line such as a wire cable or the like indicated at 132 and 134 with the lines entrained over suitable sheaves 136 and 138. Stop means in the form of a spring 141 disposed in the bottom of portion 116 limits the downward move ment of member 130 and the inward movement of the valves 126 and 128.

On admission of fuel gas through the inlet 124, the valves 12d and 128 are responsive to the gas pressure to shift outwardly along their respective arms 118 and 120 to expose such number of fuel gas apertures 122 to the fuel gas that a balance is established between the weight of member 130 and the gas pressure urging the valves outwardly. With the weight of member 130 properly established, the pressure of fuel gas escaping from the exposed fuel gas discharge apertures 122 may be maintained above any minimum amount as determined by the weight of member 130.

As with the embodiment heretofore described, the embodiment of FIG. 7 serves to maintain the pressure of the fuel gas escaping from the ports 122 despite the fact that the rate at which the fuel gas enters inlet 124 may vary widely. As with the embodiment of FIG. 1, suitable fuel gas valve means are connected in gas discharge relation with inlet 124 with such valve means responsive to the temperature of the space being heated to control the rate at which fuel gas enters the manifold through inlet 124. The burner assembly for use in conjunction with the manifold of FIG. 7 is of substantially the same construction as that heretofore described, modified slightly for use with the separate arms 118 and 120. Of course such burner assembly would be disposed in a horizontal position as distinguished from the vertical position shown in FIG. 1.

Another embodiment of my invention is shown in FIGS. 8-l0. In this embodiment not only is the fuel gas to be burned admitted to the gas manifold, but also the air supporting the fuel gas combustion is admitted. The manifold, indicated at 142, includes a burner portion extending longitudinally therealong at 144. Such burner portion is provided with an elongate slot 146 and a series of discharge apertures disposed on opposite sides of the slot in longitudinally spaced-apart relation and indicated at 148. Flame retention means in the form of a pair of channels 150 and 152 are disposed along the burner portion 144.

Slidably disposed within the manifold 142 is a pistonlike valve shown in perspective in FIG. 10 and generally indicated at 154. Such valve includes three disc-like plates 156, 158 and 16%, each of which is provided with a radially extending ear portion 162, 164 and 166, which project outwardly through the slot 146 as shown in FIG. 9. Such ear portions effectively block the escape of a fuel gas and air mixture around the valve by way of slot 146. Such ear portions are slidable along the slot as the valve 154 slides longitudinally within the manifold.

The manifold shown in FIG. 8 is disposed in a vertical position, though with modification it might be disposed horizontally as with the embodiment of FIG. 7. At the lower end the manifold is provided with an inlet connection including a mixing chamber for the air and gas indicated at 168. The fuel gas line provided with its valve for controlling the rate at which fuel gas enters the manifold is shown at 170 while at 172 is an air blower disposed in discharge relation with the inlet connection and adapted to blow air thereinto. A valve 1'74 disposed between the discharge side of blower 172 and the inlet serves to control the rate at which the air enters the manifold from the blower. Suitable means, not shown, may be connected between the gas valve in line 1713 and the air control valve 174 so that both may operate cooperatively synchonously to regulate their respective fluid flows.

The valve 154 of the FIG. 8 embodiment rises and falls within the manifold in response to variations in the pressure of the fuel gas and air mixture and serves to maintain at a uniform pressure the mixture issuing from the burner slot 146 and the pilot apertures 148. Valve 154 will control the number of apertures 148 exposed to the fuel gas and air mixture in the same fashion as the valves 126 and 128 or the valve 56 heretofore described, while the ear portions 162, 164 and 166, which project through slot 146, will control the length of the slot exposed to the fuel gas and air mixture.

While I have shown the valves 56, 126, 128 and 154 being yieldingly biased toward the inlet for the various manifolds by virtue of a weight, either the weight of the valve itself or a weighted member, such as member 131) of FIG. 7, it will become apparent to those skilled in the art that other forms of biasing means may be used. For example, spring means may be disposed between the outer end of the manifold and the sliding valve which will yieldingly urge the valve toward the fuel gas inlet. In lieu of such spring means a source of air under pressure may be admitted to the outer end of the manifold to react against the sliding valve and counterbalance the pressure of fuel gas admitted to the manifold through the inlet.

An example of the latter construction is shown schematically in FIG. 11 where the manifold 176 is disposed horizontally and is apertured at longitudinally spacedapart intervals as at 173 with a free-floating piston-like valve 18% disposed in the manifold. Fuel gas is admitted through a valve 182 to one end of the manifold by an inlet pipe 184- to react upon the piston, while at 186 an air blower serves as a source of air under pressure which enters the opposite end of the manifold through an air pressure relief valve 188 and an air inlet 1% to react against the opposite end of the piston 181 By adjusting the pressure relief of valve 1&8, the force of air pressure acting on piston when it is at the extreme right-hand position may be determined. The setting of valve 183 will in turn determine the pressure of gas entering through pipe 184 that will be necessary in order to shift the piston to expose the apertures 178 to the gas. As the piston moves to the left under the influence of gas entering through inlet 184, the gas will be maintained at a uniform pressure. Because the number of ports 178 exposed to the air pressure will be reduced as the piston moves to the left, the pressure relief valve will open to maintain the air pressure constant. A burner assembly such as that shown in FIG. 1, but disposed horizontally, and cooperatively associated with the manifold 176, receives the fuel gas from the manifold for burning.

What I claim is:

1. In a fuel gas heater, an elongate gas manifold, a gas inlet for the manifold, said manifold provided with side opening aperture means arranged longitudinally along the manifold from the inlet and through which gas may escape from the manifold, a plurality of burners with each communicating in gas-receiving relation with a portion of the length of said aperture means along the mani fold, a reciprocable piston valve element slidably supported in the manifold and yieldingly biased toward the inlet and responsive to an increase in gas pressure within the manifold to shift away from the inlet and increase the effective length of said aperture means exposed to the gas to maintain a constant gas pressure in the manifold and responsive to a decrease in the gas pressure to shift toward the inlet and reduce the effective length of said aperture means exposed to the gas whereby the number of operative burners is a function of the rate at which gas enters the manifold through said inlet, and valve means connected in gas discharge communication with said inlet to regulate the rate at which gas enters the manifold.

2. The invention as defined in claim 1 characterized in that said aperture means comprises a series of gas discharge apertures disposed at spaced-apart intervals longitudinally along the manifold, and each of said burners communicates with one of said apertures.

3. In a fuel gas heater: an upright elongate tubular fuel gas manifold provided with a plurality of longitudinally spaced-apart side-opening fuel gas discharge apertures, a free-floating reciprocable piston valve element slidably disposed in the manifold and of sufficient weight to require a predetermined fuel gas pressure therebelow to raise it, a burner assembly including a plurality of burners with each burner in fuel gas-receiving communication with one of said apertures, a fuel gas inlet for the manifold at the lower end thereof, and valve means connected in gas discharge relation with said inlet to regulate the volume of gas entering the manifold.

4. The invention as defined in claim 3 characterized in that said piston valve element comprises a spool valve having a pair of valve discs disposed spaced apart longitudinally of the manifold and connected by a stem extending between the discs, whereby fuel gas escaping around the periphery of the lower disc will discharge through said fuel gas discharge apertures in the manifold intermediate the discs.

5. The invention defined by claim 4 characterized in that said stem is hollow and adapted to receive weights for predetermining the weight of the valve element.

6. A fuel gas heater comprising, in combination: an upright elongate tubular fuel gas manifold provided with a plurality of side-opening fuel gas discharge apertures spaced apart longitudinally along the manifold, a freefioating reciprocable piston valve element slidably dis posed in the manifold and cooperating with the inner wall surface of the manifold to provide a barrier against the escape of fuel gas upwardly through the manifold and around the valve element, a burner disposed in gas-receiving relation with each aperture, said valve element of sufiicient weight to require a burner flame sustaining gas pressure within the manifold to raise the valve element to expose additional apertures to fuel gas in the manifold, and a temperature responsive gas valve coupled in gas discharge relation with the lower end of the manifold to regulate the volume of gas entering the manifold.

7. The invention as defined in claim 1 characterized in that said manifold is disposed in a vertical position with the weight of the piston valve urging the same toward the lower end of the manifold, said inlet disposed at the lower end of the manifold, and said side-opening aperture means comprising a series of gas discharge apertures disposed at spaced-apart intervals along the manifold above the inlet with said piston valve cooperating with the manifold to substantially block the escape of gas around the piston valve, whereby only those apertures between the piston valve and the inlet are exposed to gas in the manifold, and said burners are arranged vertically one above the other.

8. The invention as defined in claim 1 characterized in that means are provided in said manifold operatively connected with the piston valve and yieldingly biasing the valve toward said inlet.

9. The invention as defined in claim 8 characterized in that said means yieldingly biasing the piston valve comprises a weight carried by the valve and urging the same toward said inlet.

10. The invention as defined in claim 8- characterized in that said manifold includes a horizontal portion and a downwardly extending portion with said aperture means opening through the side of said horizontal portion, said piston valve being disposed within said horizontal portion of the manifold, a weighted member disposed for movement longitudinally within said downwardly extending portion, means connecting said weighted member to said valve whereby said Weighted member biases said valve toward the junction of the horizontal and downwardly ex tending portions of the manifold.

11. The invention as defined in claim 8 characterized in that said means yieldingly biasing the piston valve toward the inlet comprises fluid pressure generating means connected in fluid pressure discharge relation with the manifold at the opposite side of said piston valve element from said inlet, whereby fluid pressure generated by said biasing means urges the piston valve toward the inlet and gas within the manifold entering through said inlet tends to urge the valve in the opposite direction.

12. That method of controlling the firing rate of a fuel gas heater which includes a gas manifold provided with aperture m'eans opening through a side wall thereof and extending longitudinally of the manifold with a reciprocable free-floating piston valve element in the manifold 6 and with a burner assembly in gas-receiving relation with said aperture means comprising: preloading the piston valve element with a force tending to move it in one direction in the manifold suflicient to establish a head of gas pressure in the manifold for flame-sustaining combustion by the burner assembly, admitting fuel gas to the manifold at that end thereof toward which the piston valve element tends to move by said preloading, and varying the rate at which said gas is admitted to the manifold with the preloading of the piston valve element establishing the pressure of the gas in the manifold and the effective length of said aperture means.

13. In a fuel gas heater: an elongate gas manifold having an inlet at one end; means connected to the inlet for delivering gas thereto including valve mechanism for controlling the rate at which gas enters the manifold, said manifold provided with side opening aperture means arranged longitudinally along the manifold and through which gas may escape from the manifold; a gas burner arranged longitudinally along the manifold in gas-receiving relation with the aperture means, a reciprocable piston valve element slidably supported in the manifold and yieldingly biased toward the inlet end thereof and responsive to an increase in gas pressure within the manifold to shift away from the inlet end and increase the effective length of said aperture means exposed to gas in the manifold to maintain a constant gas pressure in the manifold and responsive to a decrease in the gas pressure in the manifold to shift toward the inlet and reduce the effective length of the aperture means exposed to gas in the manifold whereby the operative length of the burner is a function of the rate at which gas enters the manifold through said inlet.

14. The invention as defined in claim 13 characterized in that said aperture means comprises a slot extending longitudinally of the manifold, and said piston element includes an ear portion extending into and shiftable along the slot as the piston reciprocates in the manifold.

15. The invention as defined in claim 13 characterized in that both fuel gas and combustion air are admitted to the inlet of said manifold, and said valve mechanism is adapted to control the rate at which both the air and fuel gas are admitted to the manifold.

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5 FREDERICK L. MATTESON, JR., Primary Examiner.

MEYER. PERLIN, JAMES W. WESTHAVER,

Examiners. 

1. IN A FUEL GAS HEATER, AN ELONGATE GAS MANIFOLD, A GAS INLET FOR THE MANIFOLD, SAID MANIFOLD PROVIDED WITH SIDE OPENING APERTURE MEANS ARRANGED LONGITUDINALLY ALONG THE MANIFOLD FROM THE INLET AND THROUGH WHICH GAS MAY ESCAPE FROM THE MANIFOLD, A PLURALITY OF BURNERS WITH EACH COMMUNICATING IN GAS-RECEIVING RELATION WITH A PORTION OF THE LENGTH OF SAID APERTURE MEANS ALONG THE MANIFOLD, A RECIPROCABLE PISTON VALVE ELEMENT SLIDABLY SUPPORTED IN THE MANIFOLD AND YIELDINGLY BIASED TOWARD THE INLET AND RESPONSIVE TO AN INCREASE IN GAS PRESSURE WITHIN THE MANIFOLD TO SHIFT AWAY FROM THE INLET AND INCREASE THE EFFECTIVE LENGTH OF SAID APERTURE MEANS EXPOSED TO THE GAS TO MAINTAIN A CONSTANT GAS PRESSURE IN THE MANIFOLD AND RESPONSIVE TO A DECREASE IN THE GAS PRESSURE TO SHIFT TOWARD THE INLET AND REDUCE THE EFFECTIVE LENGTH OF SAID APERTURE MEANS EXPOSED TO THE GAS WHEREBY THE NUMBER OF OPERATIVE BURNERS IS A FUNCTION OF THE RATE AT WHICH GAS ENTERS THE MANIFOLD THROUGH SAID INLET, AND VALVE MEANS CONNECTED IN GAS DISCHARGE COMMUNICATION WITH SAID INLET TO REGULATE THE RATE AT WHICH GAS ENTERS THE MANIFOLD. 